SA387 Grade 11 Class 2 is a chromium-molybdenum alloy steel plate for high-temperature pressure vessels and boilers.
This material is widely used across multiple industries and has proven particularly effective in the oil, gas, and petrochemical sectors, where liquids and gases are frequently processed and stored under high-temperature and high-pressure conditions.The relatively higher chromium content enhances the steel's resistance to oxidation and corrosion, making SA387 Grade 11 Class 2 a reliable choice for sour gas and corrosive service environments.Its balanced mechanical properties, combined with excellent high-temperature performance, ensure long-term operational safety and structural integrity.
Equivalent Standards
| BS | EN | ASTM / ASME | DIN |
|---|---|---|---|
| 621 B | ––– | SA387-11-2 | ––– |
Chromium & Molybdenum Content
| Designation | Nominal Chromium Content (%) | Nominal Molybdenum Content (%) |
|---|---|---|
| SA387 Grade 11 | 1.25% | 0.50% |
Tensile Requirements
| Requirement | Grade 11 |
|---|---|
| Tensile Strength | 75–100 ksi [515–690 MPa] |
| Yield Strength, min (0.2% offset) | 43 ksi [310 MPa] |
| Elongation in 8 in. [200 mm], min | 18% |
| Elongation in 2 in. [50 mm], min | 22% |
| Reduction of Area, min | ––– |
Chemical Composition Requirements
| Element | Heat Analysis (%) | Product Analysis (%) |
|---|---|---|
| Carbon (C) | 0.05 – 0.17 | 0.04 – 0.17 |
| Manganese (Mn) | 0.40 – 0.65 | 0.35 – 0.73 |
| Phosphorus (P) | ≤ 0.035 | ≤ 0.035 |
| Sulphur (S) | ≤ 0.035 | ≤ 0.035 |
| Silicon (Si) | 0.50 – 0.80 | 0.44 – 0.86 |
| Chromium (Cr) | 1.00 – 1.50 | 0.94 – 1.56 |
| Molybdenum (Mo) | 0.45 – 0.65 | 0.45 – 0.70 |
Key Applications:
Petrochemical Industry:
Hydrogenation reactors, hydrocracking units, high-pressure vessels, separators, storage tanks for hydrogen-rich fluids.
Power Generation:
Boiler drums, steam headers, heat exchangers in thermal power plants, and steam turbines.
Chemical Industry:
High-temperature pressure vessels and equipment in harsh industrial settings.
Oil & Gas:
Equipment for handling sour gas (due to high Cr content) and high-temperature processing systems.
Why it's Used (Properties):
High-Temperature Strength & Creep Resistance:
Maintains structural integrity under continuous medium-high temperatures.
Corrosion & Oxidation Resistance:
Higher chromium content provides excellent resistance, crucial for aggressive environments.
Hydrogen Corrosion Resistance:
Ideal for processes involving hydrogen.
Class 2 Strength:
Offers higher yield and tensile strength than Class 1, suitable for more demanding stress conditions.
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What is the main chemical composition of SA387 Grade 11 Class 2?
Its key components include 0.05-0.17% carbon, 0.40-0.65% manganese, 1.00-1.50% chromium, and 0.45-0.65% molybdenum, ensuring its mechanical properties.
What happens if SA387 Grade 11 Class 2 is over-tempered?
Over-tempering reduces its hardness and strength, affecting load-bearing capacity. It may also cause microstructural changes leading to performance degradation.
Can SA387 Grade 11 Class 2 be used in low-temperature environments?
It is not ideal for extremely low temperatures. It performs best at -29°C to 593°C, beyond which its toughness may decrease significantly.
How to avoid machining defects in SA387 Grade 11 Class 2?
Maintain stable cutting speeds, use sharp tools, and avoid excessive heat. Proper heat treatment before machining also minimizes defects.
Can SA387 Grade 11 Class 2 be annealed?
Yes, annealing at 760-815°C and slow cooling softens the material, facilitating machining. It is often used before forming processes.
Is SA387 Grade 11 Class 2 suitable for corrosive media?
It resists mild to moderate corrosion, especially from organic acids and steam. For severe corrosion, additional coatings or alloys are needed.
What role does SA387 Grade 11 Class 2 play in petrochemical plants?
It is used to make reactor vessels, heat exchanger shells, and pipelines, handling high-temperature hydrocarbons and process fluids safely.
What is the minimum tensile strength of SA387 Grade 11 Class 2?
The minimum tensile strength is 415 MPa (60 ksi). This strength level allows it to withstand high pressure in industrial equipment operations.
Can SA387 Grade 11 Class 2 be formed by bending?
Yes, it can be bent cold or hot. Hot bending at 925-1040°C improves formability and reduces the risk of cracking during the process.
What is the maximum bending radius for SA387 Grade 11 Class 2?
The minimum bending radius depends on thickness, usually 3-5 times the material thickness for cold bending, smaller for hot bending.
What is the yield strength range of SA387 Grade 11 Class 2?
Its yield strength ranges from 205 MPa (30 ksi) to higher values depending on heat treatment. It balances ductility and load-bearing capacity effectively.